1. Field of the Invention
The present invention relates to photometry devices that measure the brightness of an object, and relates in particular to photometry devices used in automatic exposure control of a camera.
2. Description of Related Art
Japanese Laid-Open Patent Application No. 58-132735 (which corresponds to U.S. Pat. No. 4,563,069) discloses a photometry device that prohibits operation of the photometry system and the focus detection system at fixed intervals during photography and after photography. Specifically, the camera is equipped with a quick return mirror as is common, for example, in single reflex cameras. A signal is generated prohibiting photometry and focus detection, with the aim being to prevent light from reaching the photometry system and the focus detection system while the mirror is up, which occurs during release, and for predetermined time periods after the mirror is returned to the down position.
Japanese Laid-Open Patent Application No. 58-111022 (which corresponds to U.S. Pat. No. 4,657,368) discloses a single reflex camera that updates control before and after release. During continuous photography this device performs open aperture photometry before the initial release, and thereafter switches to stop-down photometry.
Because the photometry devices described above require accumulation operations to perform photometry when using an accumulating photometry element (such as, e.g., a CCD), it is necessary to continue to guide the luminous flux (i.e., light) to the photometry optical system during accumulation. However, the luminous flux may be obstructed in the course of accumulation, for example, in optical systems that have the mirror up, such as occurs during release in a single reflex camera. Even though some data was present, the data is not read, but rather is discarded, after accumulation has been interrupted. In either of the cases noted above, because the photometry data expected at the start of accumulation cannot be obtained, it is necessary to repeat the photometry operation immediately after the mirror has returned to the down position.
However, during continuous photography, the mirror may again start to go up immediately after it has gone down, and the repeated photometry operation again may become obstructed, and thus interrupted. In this case, it is not possible to perform sufficient photometry even once, and proper exposure becomes unobtainable.
In order to solve this problem, the device of U.S. Pat. No. 4,563,069 prevents erroneous photometry by prohibiting photometry while the mirror is up. However, no measures are disclosed for use when the mirror down time is short, such as occurs during continuous photography.
Although the device of U.S. Pat. No. 4,657,368 takes certain measures during continuous photography, there are no measures disclosed for use with a photometry system that uses an accumulating photometry element.